1. Field of the Invention
This invention relates to a method and apparatus for imprinting information, particularly identifying an intensifying screen used to produce a radiograph, permanently on the radiograph.
2. Description of Related Art
Each day countless numbers of radiographs are generated for medical diagnostic purposes. A radiograph of a patient's body is normally taken by a X-ray technician and the radiograph is subsequently reviewed by a radiologist for interpretation and diagnosis. Of particular concern in the interpretation of the radiograph is determining if a specific portion on the radiograph is a true representation of the X-ray exposed area of the patient's body or an irregularity induced on the film. Irregularities on the film can interfere with or cause misinterpretation of the radiograph. There are many sources from which irregularities on the film can be induced. For example, irregularities on the film can be induced from equipment or people that handle or contact the film before, during or after development of the radiographic image.
In particular, irregularities on the film can be induced from the cassette and/or the intensifying screen(s) used during the film's exposure to X-ray radiation. The layers, e.g. protective, fluorescent, etc., of X-ray intensifying screens become dented, abraded and scratched in normal use by dust and dirt, etc., such that the screens deteriorate over time and impair the image quality on a radiograph. Dust strongly adheres to the screens due to pressure exerted during sandwiching of successive film sheets between the screens. Denting is caused by a particle being forced into the surface of the screen. Repeated insertion and withdrawal of X-ray film sheets from cassettes provided with X-ray intensifying screens and the shearing action which occurs during the closing of cassettes are the principal factors which cause the abrasion of the screen surface. Also, due to the moisture permeability of the protective layers of a screen, the screens may become stained with developer and lose efficiency by preventing radiation from reaching the X-ray film. Further, the cassette itself can be the cause for irregularities in a radiograph. Typically this occurs when the cassette loses the ability to maintain intimate contact of the screens with the film, for example, due to deterioration of parts of the cassette such as a foam backing or a latching mechanism.
It is useful for a radiologist to know which cassette, and thus which intensifying screen(s), was used to produce a particular radiograph. Since many cassettes are in use by X-ray technicians it is often times very difficult to determine which cassette was used for a particular radiograph in question. It is difficult and time consuming to visually inspect cassettes for causes for irregularities since the cassettes are typically loaded and unloaded in a darkroom or by automated film handling equipment.
If the identity of a particular cassette and/or intensifying screen were imprinted on the radiograph, the cassette could be easily traced and then visually checked against the radiograph by the radiologist or pulled from circulation to repair or replace the screen and/or cassette.
It is a long standing trend in radiology to permanently place patient identification data on a radiograph. Other kinds of information which are commonly permanently imprinted on the radiograph relate to the orientation of the film and/or the patient's body when exposed to the radiation, i.e., right or left views, anterior, oblique, etc.
One method for permanently imprinting information on a radiograph is by selectively blocking portions of an X-ray film with, for example, a lead blocker in the cassette during X-ray exposure by the standard film-screen technique. The identification data is later placed within the selectively blocked portions with an identification camera which slides the blocker from that region where it had previously occluded during the X-ray exposure and flash exposes the identification data from a card onto the previously unexposed area of the film. The entire X-ray film is then developed in a routine fashion, thus permanently capturing the patient anatomical image and the identification information on the radiograph.
Other methods use X-ray opaque materials, for example lead, mercury, etc., to permanently imprint a radiograph with information during the X-ray exposure. X-ray opaque objects, such as lead letters, are secured in place, typically with tape, on a cassette in an area which will not interfere with the resultant anatomical image of the radiograph, and X-ray exposed at the same time as the patient, so that the shadow of the letters will appear on the radiograph upon development.
Thus, these methods of permanently imprinting information on a radiograph selectively block the X-ray beams during exposure to either directly imprint the desired information on the radiograph or provide an unexposed area on the film for subsequent exposure by another source.
It is an object of this invention to provide a method for permanently imprinting on a radiograph the identification of an intensifying screen and/or cassette which was used to produce the radiograph during an X-ray exposure.